With a trend toward an increasing data transfer rate of data signals, demands for a gigabit-class, high data-transfer rate exist not only in systems for communication backbones but also in systems for general consumers. In the systems for communication backbones, characteristics of transmission paths for transmitting data signals can be identified to some degrees and data transfer rates are also predetermined. Thus, the qualities of the data signal levels are substantially constant.
On the other hand, in the systems for general consumers, transmission paths have a wide variety of characteristics and various data transfer rates are also used. Thus, variations occur in the qualities of the data signal levels.
Typically, a reception apparatus for a high-speed data transfer rate has a section for detecting a data boundary portion in a data signal, a clock generation section for generating a clock corresponding to the data boundary, and a section for detecting a data signal level at the detected data boundary portion and a data signal level at a center portion of the data in accordance with the clock (e.g., refer to Japanese Laid-open Patent Publication Nos. 2003-309543 and 2004-208222.
The receiving apparatus has a analog-to-digital conversion circuit as the section for detecting the data signal level and further has a section for detecting a logic of the data signal on the basis of the data signal level.
With this configuration, when the quality of the data signal varies for each system, the result of the detection of the receiving apparatus also varies. This makes it difficult to detect the data boundary portion and to determine the logic of the data signal.